If you have an article that is in draft and is unpublished the preview link open some earlier revision of the article.
This regards the "published" link inside the editor and the "preview" link in the article listing. Either there shouldn't be a published link because the article is not published or it should at least show the latest state instead of some random earlier revision.
Since there is only one preview link in the article list you want to be able to access the draft from there.